gained 40kg in 3 years

IvoryRoseify

3 years ago i had a perfect bmi and now i am way way up there and ive been trying really hard but nothing seems to be working i dont know if im doing it right or if i need more encouragement but i cant stick to a diet for more than a week and i really need some help

i am;
-15yo
-85kg/187lbs
-160cm/5'3''

and

-my bmi is 33.2
-i need of some advice

and

i have my sisters wedding in april and i want to lose 20kg or something close to that by then (is that possible)